I. Field of the Invention
The present invention relates to an electrolytic cell hygrometer for measuring moisture levels.
II. Background Information
Electrolytic cell hygrometers are known which employ two electrodes spaced apart one from another to form a circuit pattern on a semiconductor substrate. Each electrode in effect forms one plate of a capacitor on the surface of the substrate. A film of hydroscopic electrolyte, typically, phosphorous pentoxide, is spread over the circuit pattern to fill the space between the electrodes.
Upon application of an electrical potential to the electrodes, the electrolyte, in the absence of water, does not permit current to flow between the electrodes. However, in the presence of water, the electrolyte absorbs moisture and as a consequence becomes conductive thereby permitting current to flow between the electrodes.
As the current flows between the electrodes, moisture absorbed by the electrolyte electrolyzes into hydrogen and oxygen. The electrolyte thus continuously regenerates itself. In addition, the electrical current represents an accurate measurement of the moisture absorbed in accordance with Faraday's Law of Electrolysis.
In addition, a porous membrane may be positioned over the electrodes to form a diffusion barrier between the electrolysis activity occurring in connection with the electrodes and an atmosphere whose moisture content is to be analyzed. This diffusion barrier protects the basic characteristics of the phosphorous pentoxide film and thereby improves operation of the resultant electrolytic cell hygrometer.
However, the porous membrane forming such a diffusion barrier is typically delicate and must be carefully protected. In addition, it is preferable that an electrolytic cell hygrometer employing such membrane have the capacity to not only readily replace the electrode bearing substrate, but also replace the membrane should the membrane become contaminated or if a different form of membrane is desired to be employed. Still further, it is desirable that an electrolytic cell hygrometer be compact and easy to install in an environment where moisture analysis is required.
In view of the foregoing, it is an object of the present invention to provide an electrolytic cell hygrometer of improved physical design which provides for efficient replacement of the diffusion barrier membrane and electrode carrying substrate, while maintaining a compact configuration easily mountable in an atmosphere whose moisture content is to be analyzed.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from that description or may be learned by practice of the invention.